1. Field of the Invention
This invention relates to a novel and improved medical couch. Particularly, this invention relates to a treatment couch which can be used for treating patients in radiotherapy. Still more particularly, this invention relates to a treatment couch for treating patients with X-rays and/or electrons.
2. Description of the Prior Art
Medical couches and hospital beds that incorporate mechanisms for lifting a patient are well-known in the art.
U.S. Pat. No. 346,246 discloses a medical operating couch having a lower frame and an adjustable upper frame. By turning two threaded rods, the couch top can be raised and lowered horizontally, or it can be adjusted on an incline. --Difficulties must be expected when the couch is raised from a low position since this requires considerable force, and the threaded rods and heads must be dimensioned accordingly.
U.S. Pat. No. 2,547,827 discloses a hospital bed which is vertically adjustable and universally tiltable. In this hospital bed, a motor is used to rotate a horizontally disposed shaft. Also in this design, difficulties in lifting the bed may be expected when the bed is in its lowered position. The lifting range is limited, and the lifting mechanism requires some space.
French Patent No. 1,447,701 discloses a hospital bed the top of which is also adjustable vertically; that is the top will stay in a horizontal position during and after the adjustment. --This lifting mechanism requires a special motor since it is essential that the lead screw moves through the motor. Therefore, a certain depth is needed below the motor. Such requirement is adverse to a compact design of the lifting mechanism. Also, provisions must be made that the lead screw is not positioned vertically, otherwise it would not be possible to lift the couch.
U.S. Pat. No. 3,373,453 discloses a vertically adjustable bed which contains a lower and an upper frame. --In this design, the lifting mechanism including the lower assembly is rather complex, and a large number of parts are required. Also, the maximum height which can be achieved is limited. The cross bars of the lifting mechanism are interconnected by a coil spring. If the coil spring should break, the bed may collapse very quickly. A simple coil spring, therefore, does not provide optimum security.
Other known structures such as shown in U.S. Pat. Nos. 3,611,452, 3,686,696 and 3,793,652 require an unduly and commercially undesireable large number of parts and of space in and beneath the bed to accomodate the lifting mechanism.